In an internal combustion engine, an endless chain is typically used as a transmission medium for transmitting rotation from the engine crankshaft to one or more valve-operating camshafts. The chain is in mesh with sprockets on the crankshaft and camshafts, which are of a size such as to transmit rotation from the crankshaft to camshafts at the required ratio. In such a transmission device, to ensure smooth power transmission, a lever is pressed by a tensioner into sliding contact with the traveling chain or other endless, flexible power transmission medium in order to apply appropriate tension to the medium. A side of the lever extending in the longitudinal direction forms a shoe which has a surface adapted for sliding contact with the transmission medium. The lever is pivoted at one end to the frame of an engine on a bolt, pin or the like, and a plunger of the tensioner abuts the lever near its opposite end on the side opposite the shoe.
FIGS. 7 and 8 show a lever 300 described in Japanese Patent No. 3253951. This lever comprises a lever body 301 having a shoe 302 with a surface for sliding contact with a traveling chain C, and a support 303 extending longitudinally on the back of the shoe 302 is integrally molded with the shoe, from a synthetic resin. A reinforcing plate 308 made of a rigid material fits into a longitudinally extending slot 307, the opening of which is located centrally with respect to the width of the support 303. Adjacent one end, the support 303 is provided with a mounting hole 305, through which a shaft 310 extends for pivoting the lever to the frame of an engine. The reinforcing plate 308 has a hole 308A located so that it can come into register with the mounting hole 305 when the reinforcing plate is inserted into the slot 307. The lever body 301 and the reinforcing plate 308 are held together by virtue of the fact that the shaft 310 extends through both the mounting hole 305 of the support, and the hole 308 A of the reinforcing plate.
Since the lever body comprises the shoe 302, integrally molded with the support 303 from a synthetic resin, the lever body 301 itself provides a surface on which the flexible transmission medium can slide, and it is not necessary to provide a separate shoe. As a result, the number of parts and production steps is reduced. Furthermore, since the opening of slot 307 faces in a direction perpendicular to the shoe and extends longitudinally along the lever, the reinforcing plate 308, which fits into the slot 307, increases the strength of the lever in the direction of the plane in which the pivoting movement of the lever takes place. As a result, the rigidity against bending, the toughness, and the strength, of the lever 300 is significantly improved.
In the above-mentioned lever 300, which is known as a “slide-in lever”, the lever body 301 and the reinforcing plate fitted are separately molded. Thus, the lever presents some further problems. Specifically, in order for the reinforcing plate 308 and the slot 307 conform to each other, the support 303 must be molded with a high degree of accuracy.
Another problem is that significant assembly effort is required to align the mounting hole 305 and the hole 308A of the reinforcing plate 308 during assembly.
Still another problem is the prevention of shifting of the reinforcing plate in the lever as the lever is mounted on an engine frame.
Noises are also generated at the location at which the reinforcing plate is mounted rotatably on shaft 310 and at the location at which the plunger of the tensioner abuts the reinforcing plate.
Accordingly, objects of the invention are to solve the problems of the conventional slide-in tensioner lever, and to provide a tensioner lever that does not require high molding accuracy, does not require alignment of the lever body and the reinforcing plate when the assembly is mounted on a pivot shaft, and reduces noise due to contact of the reinforcing plate with the pivot shaft and the tensioner plunger.